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dc.contributor.advisor Nicchitta, Christopher V en_US
dc.contributor.author Lacsina, Joshua Rene en_US
dc.date.accessioned 2012-05-25T20:05:14Z
dc.date.issued 2012 en_US
dc.identifier.uri http://hdl.handle.net/10161/5395
dc.description Dissertation en_US
dc.description.abstract <p>Nearly thirty percent of all newly synthesized polypeptides are targeted for rapid proteasome-mediated degradation. These rapidly degraded polypeptides (RDPs) are the primary source of antigenic substrates for the major histocompatibility complex (MHC) class I presentation pathway, allowing for the immunosurveillance of newly synthesized proteins by cytotoxic T lymphocytes. Despite the recognized role of RDPs in MHC class I presentation, it remains unclear what molecular characteristics distinguish RDPs from their more stable counterparts. It has been proposed that premature translational termination products may constitute a form of RDP; indeed, in prokaryotes translational drop-off products are normal by-products of protein synthesis and are subsequently rapidly degraded. </p><p>To study the cellular fate of premature termination products, the antibiotic puromycin was used to modulate prematurely terminated polypeptide production in human cells. At low concentrations, puromycin doubled the fraction of rapidly degraded polypeptides, with enhanced degradation predominantly affecting small polypeptides, consistent with rapid degradation of truncated translation products. Immunoprecipitation experiments using anti-puromycin antisera demonstrated that the majority of peptidyl-puromycins are rapidly degraded in a proteasome-dependent manner. Low concentrations of puromycin increased the recovery of cell surface MHC class I-peptide complexes, indicating that prematurely terminated polypeptides can be processed for presentation via the MHC I pathway. In the continued presence of puromycin, MHC I export to the cell surface was inhibited, coincident with the accumulation of polyubiquitinated proteins. The time- and dose-dependent effects of puromycin suggest that the pool of peptidyl-puromycin adducts differ in their targeting to various proteolytic pathways which, in turn, differ in the efficiency with which they access the MHC class I presentation machinery. These studies highlight the diversity of cellular proteolytic pathways necessary for the metabolism and immunosurveillance of prematurely terminated polypeptides which are, by their nature, highly heterogeneous.</p> en_US
dc.subject Pathology en_US
dc.subject Cellular biology en_US
dc.subject Immunology en_US
dc.subject major histocompatibility complex class I en_US
dc.subject proteolysis en_US
dc.subject puromycin en_US
dc.subject rapidly degraded polypeptides en_US
dc.subject termination en_US
dc.subject translation en_US
dc.title Premature Translational Termination and the Rapidly Degraded Polypeptide Pathway en_US
dc.type Dissertation en_US
dc.department Pathology en_US
duke.embargo.months 24 en_US
duke.embargo.release 2014-05-15

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